Field of the Invention
This invention relates generally to magnetoresistive tunnel junction (MTJ) and particularly to programming the MTJ.
Description of the Prior Art
Magnetic memory is due to replace conventional volatile as well as non-volatile memory soon. Efforts are underway to improve the characteristics of such memory allowing their application to widely spread.
One of the challenges of MTJs, besides manufacturing, is programming them. The MTJ stores digital information, i.e. ‘1s’ and ‘0s’, when one of its switchable magnetic layers is caused to switch in relation to its magnetization relative to one of its non-switchable magnetic layers. The resistance of the MTJ is notably different when its magnetic layers have the same magnetization (parallel) versus when they have an opposite magnetization (anti-parallel). As one would expect, the parallel state results in the MTJ having a lower resistance than the anti-parallel state. An access transistor, typically coupled to the MTJ, selects it for a read and/or programming (also referred to as “writing”). Voltage within a tolerable range is typically applied to the gate of the access transistor turning it on and off, which results in selecting, or not, the MTJ for read/write operations.
There are multiple techniques for reading and programming the MTJ, however, all of them suffer from lack of reliability or reliability that can stand the test of the MTJ a a solid working memory that can replace conventional memory. Reliability is an issue, at least in part, because the probability of overlap between the voltage of one magnetic state (parallel) and the voltage of the other magnetic state (anti-parallel) is extensive enough to result in an intolerable number of errors when reading the MTJ.
Thus, a need arises for reliably reading and programming a MTJ.